Éditeur(s) : Elsevier Sci Ltd
Résumé : The aim of this study is to establish a baseline for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) lifetime prediction in a marine environment, by means of mechanical and physico-chemical characterization of specimens immersed in continuously renewed and filtered natural seawater in the laboratory at different temperatures (4, 25 and 40°C). Samples were also aged at sea in Lorient harbour in order to compare laboratory and natural degradation mechanisms and kinetics. Due to its morphology, hydrolysis of PHBV in natural seawater is quite slow, and samples were observed to undergo preferentially an enzymatic surface degradation. Increasing the aging temperature in the laboratory promotes the water uptake and causes hydrolysis. As two degradation mechanisms occur in parallel, the choice of test conditions is critical, and the lifetime of PHBV in a marine environment is difficult to predict accurately.
Polymer Degradation And Stability (0141-3910) (Elsevier Sci Ltd), 2014-07 , Vol. 105 , P. 237-247

Droits : 2014 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00188/29972/28425.pdf
DOI:10.1016/j.polymdegradstab.2014.04.026
http://archimer.ifremer.fr/doc/00188/29972/

Éditeur(s) : HAL CCSD
Résumé : National audience
Les lherzolites de l’étang de Lherz, de Freychinède et de Berqué sontassociées à des métasédiments détritiques contenant des fragments dominantsde manteau et de marbres issus du démantèlement de la couverturemétamorphique mésozoïque de la Zone Nord-Pyrénéenne(ZNP).Les relations originelles entre le socle ultrabasique et ces brèches etmicrobèches ne sont pas toujours accessibles, mais on peut observeren quelques endroits des caractères de contacts sédimentaires (surfaceirrégulière, anfractuosités emplies de microbrèches, remaniement dela lherzolite serpentinisée). La matrice des brèches est invariablementconstituée de grains issus du démantèlement du manteau serpentiniséou non (Ol, CPX, OPX, spinelles, serpentines). Ce cortège ultrabasiqueest associé à des fragments de marbres souvent foliés portant déjàl’empreinte du métamorphisme HT pyrénéen. On trouve également engrande quantité de petites phyllites dont l’origine est soit détritique, soitmétamorphique, par cuisson de la brèche lors d’un stade tardif métamorphismeHT crétacé. Sur le corps de Lherz, la composition des clastes desbrèches évolue entre un pôle 100% carbonaté et un pôle 100% ultrabasique.Par endroit, les carbonates envahissent la péridotite serpentiniséequi prend alors l’aspect typique des ophicalcites. En plusieurs points,à la périphérie immédiate des corps de Lherz et de Freychinède et dansles fentes au sein des lherzolites de Berqué, affleurent les roches à saphirine(voir Monchoux, 1973) faites de lits de minéraux souvent bien triéset de microbrèches dont la composition, surprenante, associe un cortègeultrabasique à un cortège singulier de débris de métaévaporites etde métaophites (phlogopites, anthophyllites, enstatites, hornblendes,...).La mise à nu du manteau dans la ZNP au Crétacé s’accompagne doncdu démantèlement de toute la couverture métamorphique prérift, depuisle Trias jusqu’au Crétacé. Cette contrainte est intégrée dans le modèled’exhumation proposé pour cette partie de la ZNP. Ce modèle tente derendre compte également de la présence au sein du corps principal desbrèches de Lherz (vallon de Fontête Rouge) de rares fragments d’uncroûte continentale à affinité granulitique
24 ème Réunion des sciences de la Terre 2014
Pau, France

insu-01080835
https://hal-insu.archives-ouvertes.fr/insu-01080835

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Amelotin (AMTN) is an ameloblast-secreted protein that belongs to the secretory calcium-binding phosphoprotein family, which also includes the enamel matrix proteins amelogenin, ameloblastin and enamelin. Although AMTN is supposed to play an important role in enamel formation, data were long limited to the rodents, in which it is expressed during the maturation stage. Recent comparative studies in sauropsids and amphibians revealed that (i) AMTN was expressed earlier, i.e. as soon as ameloblasts are depositing the enamel matrix, and (ii) AMTN structure was different, a change which mostly resulted from an intraexonic splicing in the large exon 8 of an ancestral mammal. The present study was performed to know whether the differences in AMTN structure and expression in rodents compared to non-mammalian tetrapods dated back to an early ancestral mammal or were acquired later in mammalian evolution. We sequenced, assembled and screened the jaw transcriptome of a neonate opossum Monodelphis domestica, a marsupial. We found two AMTN transcripts. Variant 1, representing 70.8% of AMTN transcripts, displayed the structure known in rodents, whereas variant 2 (29.2%) exhibited the nonmammalian tetrapod structure. Then, we studied AMTN expression during amelogenesis in a neonate specimen. We obtained similar data as those reported in rodents. These findings indicate that more than 180 million years ago, before the divergence of marsupials and placentals, changes occurred in AMTN function and structure. The spatiotemporal expression was delayed to the maturation stage of amelogenesis and the intraexonic splicing gave rise to isoform 1, encoded by variant 1 and lacking the RGD motif. The ancestral isoform 2, housing the RGD, was initially conserved, as demonstrated here in a marsupial, then secondarily lost in the placental lineages. These findings bring new elements towards our understanding of the non-prismatic to prismatic enamel transition that occurred at the onset of mammals.
ISSN: 1932-6203

Droits : http://creativecommons.org/licenses/by/
hal-01233552
https://hal.archives-ouvertes.fr/hal-01233552
https://hal.archives-ouvertes.fr/hal-01233552/document
https://hal.archives-ouvertes.fr/hal-01233552/file/journal.pone.0133314.pdf
DOI : 10.1371/journal.pone.0133314

Éditeur(s) : HAL CCSD
Résumé : International audience
Up-to-date estimates of the health outcomes of preterm children are needed for assessing perinatal care, informing parents, making decisions about care, and providing evidence for clinical guidelines. To determine survival and neonatal morbidity of infants born from 22 through 34 completed weeks' gestation in France in 2011 and compare these outcomes with a comparable cohort in 1997. The EPIPAGE-2 study is a national, prospective, population-based cohort study conducted in all maternity and neonatal units in France in 2011. A total of 2205 births (stillbirths and live births) and terminations of pregnancy at 22 through 26 weeks' gestation, 3257 at 27 through 31 weeks, and 1234 at 32 through 34 weeks were studied. Cohort data were collected from January 1 through December 31, 1997, and from March 28 through December 31, 2011. Analyses for 1997 were run for the entire year and then separately for April to December; the rates for survival and morbidities did not differ. Data are therefore presented for the whole year in 1997 and the 8-month and 6-month periods in 2011. Survival to discharge and survival without any of the following adverse outcomes: grade III or IV intraventricular hemorrhage, cystic periventricular leukomalacia, severe bronchopulmonary dysplasia, retinopathy of prematurity (stage 3 or higher), or necrotizing enterocolitis (stages 2-3). A total of 0.7% of infants born before 24 weeks' gestation survived to discharge: 31.2% of those born at 24 weeks, 59.1% at 25 weeks, and 75.3% at 26 weeks. Survival rates were 93.6% at 27 through 31 weeks and 98.9% at 32 through 34 weeks. Infants discharged home without severe neonatal morbidity represented 0% at 23 weeks, 11.6% at 24 weeks, 30.0% at 25 weeks, 47.5% at 26 weeks, 81.3% at 27 through 31 weeks, and 96.8% at 32 through 34 weeks. Compared with 1997, the proportion of infants surviving without severe morbidity in 2011 increased by 14.4% (P < .001) at 25 through 29 weeks and 6% (P < .001) at 30 through 31 weeks but did not change appreciably for those born at less than 25 weeks. The rates of antenatal corticosteroid use, induced preterm deliveries, cesarean deliveries, and surfactant use increased significantly in all gestational-age groups, except at 22 through 23 weeks. The substantial improvement in survival in France for newborns born at 25 through 31 weeks' gestation was accompanied by an important reduction in severe morbidity, but survival remained rare before 25 weeks. Although improvement in survival at extremely low gestational age may be possible, its effect on long-term outcomes requires further studies. The long-term results of the EPIPAGE-2 study will be informative in this regard.
ISSN: 2168-6211

hal-01258705
http://hal.univ-brest.fr/hal-01258705
PUBMED : 25621457
DOI : 10.1001/jamapediatrics.2014.3351